13.4

Challenges in the Development of Nanodrugs

for Nephrolithiasis

The adult human kidney contains several nephrons which consist of two filtration

units, the glomerulus filtration and hairpin-shaped tubule composed of a proximal

tubule, the loop of Henle, a distal tubule and collecting duct (Kamaly et al. 2016).

Under normal conditions, the glomerulus barrier filters blood on the basis of size and

charge and ensures that only water and small solutes (urea, glucose, amino acids, and

mineral ions) pass into the urine from the plasma and all the high molecular-weight

plasma components such as erythrocytes and negatively charged components like

albumin are retained in the blood (Eaton and Pooler 2013). In order to be delivered in

the kidneys, NPs must be tiny enough to cross the glomerulus filtration barrier.

Several organizational attributes of the glomerulus filtration unit such as the enlarged

endothelial gaps can be utilized for transportation of NPs into kidney cells and

various components. The size of the NPs remains among the major challenges while

designing nanomedicines for kidney stones. Usually most of the NPs fall in the range

of 30–150 nm and are not liable for filtration through the kidneys into the urine

unless degraded into a size less than 10 nm. Colloids and particles in the range of

5–7 nm of hydrodynamic diameter can pass through the glomerulus and can be

excreted, i.e., they fall below the kidney filtration threshold in healthy adults

(Rahman et al. 2017). For inorganic NPs, a deviation from this range to 12–16 nm

has been observed. This proposes an individual investigation of the renal clearance

Fig. 13.2 Nanoparticles used

to design nanodrugs for

treating kidney stones

13

Nanodrugs: A Futuristic Approach for Treating Nephrolithiasis

207